# Relationship history for MSHA mine 4703916

Current hierarchy: **Blair E  Dillman → Prairie Sand and Gravel, Inc. → Masaba Washplant**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Blair E  Dillman → Masaba Washplant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Prairie Sand and Gravel, Inc. → Masaba Washplant; 2022-01-24 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Blair E  Dillman → Prairie Sand and Gravel, Inc.; 2022-01-24 to current/open; source msha-controller-operator-history